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A former USC professor sought on child sex charges has been brought back to Los Angeles after being arrested in Mexico. Walter Lee Williams had recently been added to the FBI's Ten Most Wanted List. Beverly White reports for the NBC4 News at 11 p.m. on June 19, 2013. (Published Thursday, June 20, 2013)

It took investigators two years to build a case against a former USC professor who was arrested in Mexico Tuesday, a day after he was named to the FBI's 10 Most Wanted fugitives list for alleged child-sex crimes.

Walter Lee Williams, 64, had been indicted in April on charges of sexual exploitation of children and traveling abroad for the purpose of engaging in sexual acts with children.

Williams is accused of traveling from Los Angeles to the Philippines in January 2011 to engage in sex acts with two 14-year-old boys and taking sexually explicit pictures of one of them. He allegedly met the two boys online in 2010 and had Internet webcam sessions with them

He was arrested in the resort city of Playa del Carmen in Mexico, where he offered no resistance, FBI and Los Angeles Police Department officials said at a news conference Wednesday.

Williams returned to Los Angeles late Wednesday, escorted through LAX by several federal agents.

Prosecutor Gaspar Armando Garcia Torres told the Associated Press that Williams was captured late Tuesday while drinking coffee near a park in the Caribbean beach town.

Bill Lewis, the assistant director in charge of the FBI's Los Angeles Field Office, said at the Wednesday news conference that it was Williams' addition to the FBI’s Ten Most Wanted Fugitives list Monday -- and resulting media attention -- that led to Williams' capture.

Lewis said a Mexican citizen recognized Williams as a wanted fugitive from a photograph in a newspaper.

"It was just a short 48 hours ago that we stood in front of the media and talked about this heinous individual and the need for his capture," LAPD Assistant Chief Michel Moore said during the news conference.

"This is a good day in Los Angeles because two years ago, an investigation started from a citizen who was concerned about this man’s intentions of attacking and molesting young men, young children, young boys. ... We look forward to him being held accountable for his acts."

Authorities believe the case assembled by an LAPD detective and an FBI agent against Williams prompted the suspect to flee the country, Moore said.

"He fled and we have been hunting for him since," Moore said.

Moore said the investigation began after an "adult student" contacted a crime hotline with suspicions about Williams.

"He began having conversations over the Internet with Mr. Williams, and he believes through the course of those interactions that Mr. Williams was grooming or interested in having sex with young boys -- those suspicions were brought to the department," Moore said.

A break in the case came when an FBI agent found child pornography on a computer that Williams had with him when returning to the United States at Los Angeles International Airport, Moore said.

"It has been a two-year investigation because it's been a matter of putting a puzzle together, all of which has not been offered by Mr. Williams," Moore said.

Williams, pictured below at right, was a tenured professor of anthropology, history and gender studies at the University of Southern California. According to a profile that has since been removed from the USC website, Williams was a founding editor of the International Gay & Lesbian Review and also taught at the University of California, Los Angeles, in the 1980s.

The FBI said Williams preyed upon boys between ages 14 and 17, many of whom live in economically underdeveloped countries.

Moore said investigators believe there are additional victims, and he asked them to come forward. Lewis said there were no known victims in the Los Angeles area.

Lewis said investigators would attempt to build a timeline of Williams' whereabouts so that they could find victims.

“Because of his status, he has the means and access to children, and that’s what makes him dangerous,” said FBI Special Agent Jeff Yesensky in a video released by the agency before Williams' capture. “He preys on the most vulnerable children.”

Williams was charged in Los Angeles on April 30 with one count of producing child pornography, one count of traveling for the purpose of engaging in illicit sexual conduct with a minor and two counts of engaging in illicit sexual conduct in foreign places.

The FBI had offered a reward of up to $100,000 for information leading directly to Williams’ arrest.

He is a former Palm Springs resident with an extensive history of travel through Southeast Asia -- specifically the Philippines -- and may haved traveled to Mexico and Peru, the FBI said. Williams is also affiliated with the Buddhist Universal Association in Los Angeles.